As the technology progresses, the smart phone become ubiquitous and the number of pixels of the camera in the smart phone greatly increases. Because the camera of the smart phone features a digital sensor to form imaging, the sensor quality is greatly related to the photo quality. If dust or any foreign objects falls on the sensor, the dust or the foreign objects will also appear in the photo. In addition, the demands on the cleanliness of the key parts of the camera module upgrade become higher as the number of pixels of the camera increases. In particular, special concerns are emphasized over the dust and external pollutions caused by the mechanical motion of the voice coil motor or during manufacturing.
FIG. 1A shows a cross-sectional view of a known lens driving device, and FIG. 1B shows a schematic view of detailed structure and motion of FIG. 1A. As shown in FIG. 1A, a lens driving device 10 includes a lens assembly 11, a lens carrier base 12, an upper cover 13, a bottom 14, and a sensor element 15. The lens carrier base 12 is for housing the lens assembly 11, which is loaded into the lens carrier base 12 through screw threads. The lens carrier base 12 is connected to the bottom 14 through a plurality of resilient elements (not shown). The upper cover 13 is disposed outside of the lens carrier base 12 and is fixed to the bottom 14. The sensor element 15 is disposed underneath the lens assembly 11. The lens carrier base 12 is able to move back and forth along the Z direction for the focusing of the lens assembly 11.
As shown in FIG. 1B, when the lens carrier base 12 moves the lens assembly 11 towards Z direction for focusing, a gap 16 is formed between the lens carrier base 12 and bottom 14, and foreign objects 17 may fall on the sensor element 15 through the gap 16, which results in dots or other shadows on the photo taken by the sensor element 15.